Trigger warnings about suicide, depression, gaslighting, manipulation, taking advantage of a minor, and many other topics. If you're affected by any of these, please do not read this manga. - - - Story The plot and the setting is pretty straightforward for this manga at the start before it becomes a crazy convoluted shit show of edgyness. You have a 17 year old named Reiji in a small town that he can't leave because of his responsibilities and his duty to his family. This is established right in the first chapter, that Reiji lives in his own "abyss". However, we are soon introduced to the other members of the cast, the "understanding" teacher, the "kind yet troubled" mother, the "loveable" friend, and the "bully" childhood friend. And slowly as the plot unravels you realize that all of these characters have much more to them - much more sinister, than what the plot lets on (not in a good way).
It feels like if you took Oyasumi Punpun's suffering and cranked it up to 11 just for the sake of it. Some might like it, some might not, really depends on the reader and what kind of kinks and fetish they have because this is not something the average person would enjoy in any way unless they have some sick fetish. - - -Art The art is the only good thing about Shounen no Abyss and Minenami Ryo has proven themself as a good artist with Hatsukoi Zombie, and while that series was a ecchi romcom, this series has much darker moments, right from the start. The cover page of the first chapter is good enough to set the tone for the series overall. The characters are drawn to be cute and waifu'd up to look cute and appeal to the reader. That's how the series pulls you in. However, the art apart from that is nothing too special, it doesn't have those "sakuga" moments that Punpun has where the art is just really good, and you download it to use as a wallpaper. It does have excellent cover pages though. - - -Characters The reader is provided with a range of characters, and outside of Reiji himself and perhaps Chako, most of them are very "messed up in the head".
The protagonist Reiji is meant to be a relatable depressed character. He has no dreams, no hopes, nothing because he has to take care of his grandmother and older brother who is a NEET and support his mother. The following panel sums it up rather well. The "Abyss" as the title implies is the depressing life that Reiji is stuck forever in. This can be disturbing to read for some people so it is highly advised to not read this if you're not in a healthy state of mind and/or if you get affected by the media that you consume.
There are other characters in the series, and I won't spoil any of the plot twists that might come for those characters.
There is Nagi Aoe, an idol that is somehow in the rural town.
Sakuko Akiyama or "Chako" - the character that cares for Reiji and has dreams of going to Tokyo.
Yuko Kurose - Reiji's mom and a hardworking nurse, who is trying her best to support her family.
Yuri Shibasawa - Reiji's homeroom teacher, a kind and understanding person.
Gen Minegishi - Reiji's childhood friend, he's similar to Bakugo from BNHA to some extent.
Kousaku Esemori - the writer of a story in the series called "Lover's Abyss". - - -Enjoyment I really do not have much to say in regards to this. This is a messed up series, that you can enjoy from just the POV of the characters. I enjoyed it upto chapter 60 but afterwards it has become stale and pointless, some might still enjoy it as with every manga (subjective medium with subjective opinions) but I cannot say that I enjoy reading it anymore as much as I did for the first 60 chapters. It feels like a fetish/kink content with all the sexual assault and manipulation into having minors have sex or taking advantage of them. The series makes me feel sick with how it is written. I am sure some people will excuse it as "oh it's just fiction" but I really have to ask what the hell is wrong with the author that they're writing this shit. Like what is going on inside their head to write up something this sick and messed up. - - -Overall I think this series can be best described as a dumpster that is on fire rolling down multiple flights of stairs because how shit it is. The writing is extremely convoluted and super edgy to the point that some elements only exist to be edgy. Like sexual assault, or grooming a minor, manipulating a minor into having sex with you. The series is just edgy beyond belief and I have a strong feeling that the author is letting out their repressed fucked up thoughts with this manga because most of the edgy topics have no reason to really exist.